Field of the Invention
The invention relates to a method for planning a brachytherapy treatment and to a radiation treatment planning system.
Description of the Prior Art
In a brachytherapy, also called internal radiation therapy, short-distance radiation therapy or therapy with enclosed radiation sources, radiation sources that include radioactive substances are introduced into a patient's body in order to damage or destroy target tissue, for example tumors, by radiation locally in the patient's body. In such cases the radiation load for healthy tissue can be minimized because the radiation sources can contain radioactive substances with a short radiation range, for example beta radiators of gamma radiators of low energy. Furthermore the irradiation is carried out locally from within the body and does not, as is the case for example with an external radiation therapy by means of a linear accelerator, first have to penetrate through to the target tissue from outside the body through healthy tissue. The radiation sources are typically introduced into the body by means of at least one applicator, often by multiple applicators.
Radiation sources permanently implanted in the body can be used for brachytherapy. These permanently implanted radiation sources are typically implanted by applicators embodied as capsules, also called seeds, in the vicinity of the target tissue. This type of brachytherapy uses radiation sources having a low dose rate, typically below 2 Gray per hour. Such brachytherapy is also called Low-Dose-Rate brachytherapy (LDR brachytherapy).
As an alternative, at least one applicator embodied as a hollow needle and/or catheter can be implanted in the body in the vicinity of the target tissue for the brachytherapy. Temporary radiation sources, typically with a high dose rate, typically greater than 12 Gray per hour, can then be introduced through such a needle or catheter. This method is also called High-Dose-Rate brachytherapy (HDR brachytherapy).
For a brachytherapy treatment, especially when the at least one applicator is implanted in the body, a radiation treatment plan is typically created. This radiation treatment plan designates, for example, for how long and/or how often, in HDR brachytherapy, the radiation sources should remain in the vicinity of the target tissue. As an alternative or in addition, the radiation treatment plan can provide a recommendation for an implantation of further applicators, especially for an LDR brachytherapy. Naturally the radiation treatment plan can also provide for further measures appearing sensible to those skilled in the art.
A dose calculation, especially if the at least one applicator is already implanted into the body, is typically required for creating the radiation treatment plan. In such cases an especially precise knowledge about the position of the at least one applicator, especially in relation to the target tissue and/or surrounding tissue is required for the dose calculation. Surrounding tissue can include radiation-sensitive organs at risk (OAR), that are not intended for irradiation.